The present invention relates to noxious-insect repellents comprising a compound which is substantially odorless and has an extremely excellent noxious-insect repelling effect and durability.
As a noxious-insect repellent for protecting bodies from noxious-insects such as mosquitoes, flies and the like, a preparation applied to the skin which contains N,N-diethyltoluamide has so far been extensively used. Additionally, it has been known that p-menthane-3,8-diol and 8-hydroxy-p-menthan-3-one have a strong insect-repelling effect (Japanese Patent Application Kokai Nos. 60-199,804 and 5-173,104) and that 2-ethyl-1,3-hexanediol and 2-(1-hydroxyethyl)-cyclohexanol also have a similar repelling effect (U.S. Pat. No. 2,407,205). However, problems have been posed such that N,N-diethyltoluamide has a peculiar offensive odor and p-menthane-3,8-diol, 8-hydroxy-p-menthan-3-one, 2-ethyl-1,3-hexanediol or 2-(1-hydroxyethyl)-cyclohexanol lacks durability. Therefore, development of novel noxious-insect repellents has been expected.
The present invention has been accomplished under these circumstances. The object of the present invention is to provide noxious-insect repellents which have no peculiar offensive odor and exhibit an excellent noxious-insect repelling effect and durability.
We, the inventors, as a result of assiduous studies conducted in order to achieve the above object, have succeeded in synthesizing substantially odorless compounds having an excellent noxious-insect repelling effect and durability, and thus accomplished the present invention.
Namely, the first embodiment of the present invention is a noxious-insect repellent which contains 0.1-90% by weight, based on the total weight, of at least one of 2-(1-hydroxy-alkyl)-cycloalkanols represented by the following general structural formula (1): 
wherein n is an integer of 3-10, R1 is hydrogen or a straight-chain saturated hydrocarbon radical having 1-6 carbon atoms; R2 is hydrogen or methyl group; Rm represents m of the same or different, straight-chain or branched, saturated or unsaturated, hydrocarbon radicals R which, as a substituent group, can be bonded to carbocyclic atoms; m is an integer of 0-8, provided that m should be at least 1 when either one of R1 or R2 is an alkyl group and m should be at least 2 when both the R1 and R2 are alkyl groups; the sum of the carbon atoms of Rm does not exceed 8; and, further, when n is 4, R may by an isopropylidene group which intramolecularly bridges between the third and sixth carbocyclic atoms.
Among the above 2-(1-hydroxyalkyl)-cycloalkanols, preferred are 2-(1-hydroxyisopropyl)-5-methyl-cyclohexanol derivatives represented by the following general structural formula (2): 
wherein R3 is a straight-chain or branched, saturated or unsaturated, hydrocarbon radical having 1-8 carbon atoms; 2-(1-hydroxyisopropyl)-5,6-dimethyl-cyclohexanol represented by the following chemical structural formula (3): 
2-(1-hydroxyisopropyl)-5-methyl-6-methylene-cyclohexanol represented by the following chemical structural formula (4): 
and, 2-(1-hydroxyalkyl)-cycloalkanols represented by the following general structural formula (5): 
wherein n, m, Rm and R1 are the same as above; particularly, 2-(hydroxymethyl)-cycloalkanols represented by the following general structural formula (6): 
wherein n, m and Rm are the same as above; and inter alia 2-(hydroxymethyl)-3-methyl-6-isopropyl-cyclohexanol represented by the following chemical structural formula (7): 
Furthermore, among the 2-(1-hydroxyalkyl)-cyclo-alkanols represented by the general structural formula (5), particularly preferred are 2-(1-hydroxymethyl)-cyclohexanol derivatives represented by the following general structural formula (8): 
wherein R4 is a straight-chain or branched, saturated or unsaturated, hydrocarbon radical having 1-8 carbon atoms; and 2-(1-hydroxymethyl)-cyclopentanol derivatives represented by the following general structural formula (9): 
wherein R4 is the same as above.
Furthermore, preferred examples of the present invention include 3-(1-hydroxyalkyl)-borneol derivatives represented by the following general structural formula (10) which, in the 2-(1-hydroxyalkyl)-cycloalkanols represented by the general structural formula (1), is specified by defining n as 4 to form a 6-membered carbocycle and Rm as an isopropylidene group intramolecularly bridging between the third and sixth carbocyclic atoms: 
wherein R5 and R6 are hydrogens or lower alkyl groups having at most 3 carbon atoms and the sum of the carbon atoms of R5 and R6 is 0-3.
The most preferable noxious-insect repellents of the above first embodiment of the present invention contain 0.1-90%, preferably 3-20%, by weight, based on the total weight, of at least one compound selected from the group consisting of the 2-(1-hydroxyalkyl)-cycloalkanols represented by the formulae (2), (3), (4), (5), (6), (7), (8), (9) and (10).
The second embodiment of the present invention is a noxious-insect repellent which contains 0.1-90% by weight, based on the total weight, of at least one of 2-(1-hydroxyalkyl)-cycloalkanones represented by the following general structural formula (11): 
wherein n, R1 and R2 are the same as above; Rmxe2x80x2 represents mxe2x80x2 of the same or different, straight-chain or branched, saturated or unsaturated, hydrocarbon radicals R which, as a substituent group, can be bonded to carbocyclic atoms; mxe2x80x2 is an integer of 0-8, provided that mxe2x80x2 should be at least 2 when n is at least 4 and both the R1 and R2 are alkyl groups; the sum of the carbon atoms of Rmxe2x80x2 does not exceed 12; and, further, when n is 4, R may be an isopropylidine group which intramolecularly bridges between the third and sixth carbocyclic atoms.
Among the above compounds represented by the formula (11) that are contained in the noxious-insect repellents, preferably used are 2-(1-hydroxyisopropyl)-cycloalkanone derivatives represented by the following general structural formula (12): 
wherein nxe2x80x2 is an integer of 3 or 4; when nxe2x80x2 is 3, mxe2x80x2 is at least 1; and when nxe2x80x2 is 4, mxe2x80x2 is at least 2.
Among the 2-(1-hydroxyisopropyl)-cycloalkanone derivatives represented by the above formula (12), further particularly preferred is 2-(1-hydroxyisopropyl)-5-methyl-cyclopentanone represented by the following chemical formula (13) and 2-(1-hydroxyisopropyl)-5-methyl-cyclohexanone derivatives represented by the following chemical formula (14): 
wherein R3 is the same as above.
Among the 2-(1-hydroxyalkyl)-cycloalkanones represented by the above general structural formula (11), further preferred are 2-(1-hydroxyalkyl)-cycloalkanones represented by the following general structural formula (15) and 2-(hydroxymethyl)-cycloalkanones represented by the following general structural formula (16), particularly, 2-(1-hydroxymethyl)-3-methyl-6-isopropyl-cyclohexanone represented by the following chemical structural formula (17): 
wherein n, mxe2x80x2, Rmxe2x80x2 and R1 are the same as above; 
wherein n, mxe2x80x2 and Rmxe2x80x2 are the same as above; and 
The preferred examples of the present invention include 3-(1-hydroxyalkyl)-camphor derivatives represented by the following general structural formula (18) which, in the 2-(1-hydroxyalkyl)-cycloalkanones represented by the foregoing general formula (11), is specified by defining n as 4 to form a 6-membered carbocycle and Rmxe2x80x2 as an isopropylidene group intramolecularly bridging between the third and sixth carbocyclic atoms: 
wherein R5 and R6 are the same as above.
The most preferred second embodiment of the present invention are noxious-insect repellents containing 0.1-90%, preferably 3-20%, by weight, based on the total weight, of at least one compound selected from the group consisting of the compounds represented by the above chemical structural formulae (12), (13), (14), (15), (16), (17) and (18).
The construction of the present invention will be explained in detail hereinafter.
The 2-(1-hydroxyisopropyl)-5,6-dimethyl-cyclohexanol shown by the chemical structural formula (3) which falls in the scope of the above general structural formulae (1) and (2), that is, p-menthane-2-methyl-3,8-diol (referred to as xe2x80x9cMMDxe2x80x9d hereinafter), can be obtained by admixing 2,3,7-trimethyl-6-octenal (referred to as xe2x80x9cTOxe2x80x9d hereinafter) with an aqueous solution of an acid, such as sulfuric acid or the like, while stirring. Alternatively, the 2-(1-hydroxyisopropyl)-5-methyl-6-methylene-cyclohexanol shown by the chemical structural formula (4), that is, p-menthane-2-methylene-3,8-diol (referred to as xe2x80x9cMMEDxe2x80x9d hereinafter), can be obtained by admixing 3,7-dimethyl-2-methylene-6-octenal (referred to as xe2x80x9cDMOxe2x80x9d hereinafter) with an aqueous solution of an acid such as sulfuric acid or the like, while stirring.
It has been known that both the 2,3,7-trimethyl-6-octenal (TO) and 3,7-dimethyl-2-methylene-6-octenal (DMO) are compounds which can easily be obtained from citronellal (U.S. Pat. No. 3,463,818). Both the MMD and MMED obtained by the above synthesizing process are colorless, transparent, oily substances having substantially no odor.
The 2-(1-hydroxyisopropyl)-5-methyl-cyclohexanol derivatives shown by the general structural formula (2), which are used in the present invention, i.e., p-menthane-2-alkyl-3,8-diol derivatives, can be obtained by admixing 2-alkyl-3,7-dimethyl-6-octenal with an aqueous solution of an acid such as sulfuric acid or the like, while stirring. It has been known that the 2-alkyl-3,7-dimethyl-6-octenal, which is a starting material for producing the p-menthane-2-alkyl-3,8-diol, can easily be obtained from citronellal (Summary Report of Lectures, presented in 35th Symposium on Perfume, Terpene and Essential Oil Chemistry, p. 62, 1991).
The p-menthane-2-alkyl-3,8-diol derivatives obtained by the above synthesizing process are colorless, transparent, oily substances having substantially no odor.
The above p-menthane-2-alkyl-3,8-diol derivatives include, for example:
p-menthane-2-ethyl-3,8-diol,
p-menthane-2-propyl-3,8-diol,
p-menthane-2-butyl-3,8-diol,
p-menthane-2-pentyl-3,8-diol,
p-menthane-2-hexyl-3,8-diol,
p-menthane-2-isopropyl-3,8-diol,
p-menthane-2-(3-methylbutyl)-3,8-diol,
p-menthane-2-(2-propenyl)-3,8-diol,
p-menthane-2-(3-butenyl)-3,8-diol,
p-menthane-2-(cis-3-hexenyl)-3,8-diol,
p-menthane-2-octyl-3,8-diol,
and the like.
The 2-hydroxymethyl-2-alkyl-cyclohexanols shown by the general formula (8) falling in the scope of the 2-(1-hydroxyalkyl)-cycloalkanol derivatives shown by the above general structural formula (1), which are applied in the present invention, can be produced by a manufacturing process wherein 2-ethoxycarbonyl cyclohexanone obtained from cyclohexanone by a conventional process is reacted with an alkylbromide to provide 2-ethoxycarbonyl-2-alkyl-cyclohexanone which is then reduced by using lithium borohydride as a reducing agent (Organic Synthesis, Vol. 47, p. 20, 1967).
The 2-hydroxymethyl-cyclohexanol derivatives obtained by the above synthesizing process are colorless, transparent, oily substances having substantially no odor.
The 2-hydroxymethyl-cyclohexanol derivatives to be employed in the present invention include compounds derived by adding a saturated straight-chain or branched alkyl group having 1-12 carbon atoms to the second carbocyclic atom of a 2-hydroxymethyl-cyclohexanol, such as:
2-hydroxymethyl-2-methyl-cyclohexanol,
2-hydroxymethyl-2-ethyl-cyclohexanol,
2-hydroxymethyl-2-propyl-cyclohexanol,
2-hydroxymethyl-2-isopropyl-cyclohexanol,
2-hydroxymethyl-2-butyl-cyclohexanol,
2-hydroxymethyl-2-hexyl-cyclohexanol,
2-hydroxymethyl-2-octyl-cyclohexanol,
2-hydroxymethyl-2-decyl-cyclohexanol,
2-hydroxymethyl-2-dodecyl-cyclohexanol,
and the like.
The substituent alkyl group at the second carbon atom is preferred to have about 1-8 carbon atoms in view of the volatility of the compounds.
The 2-hydroxymethyl-2-alkyl-cyclopentanols shown by the general formula (9) falling in the scope of the 2-(1-hydroxyalkyl)-cyclopentanol derivatives shown by the above general structural formula (1), which are applied in the present invention, can be produced by a manufacturing process wherein 2-ethoxycarbonyl-cyclopentanone obtained from cyclopentanone by a conventional process is reacted with an alkylbromide to provide 2-ethoxycarbonyl-2-alkyl-cyclopentanone which is then reduced by using lithium borohydride as a reducing agent (Organic Synthesis, Vol. 47, p. 20, 1967).
It has been reported that 2-hydroxy-2-nonyl-cyclopentanol, as an intermediate of synthesis, was isolated by the above process. However, there has never been disclosed that this compound has a noxious-insect repelling effect (Chem. Pharm. Bull., p. 3047, Vol. 29, 1981).
The 2-hydroxymethyl-cyclopentanol derivatives obtained by the above synthesizing process are colorless, transparent, oily substances having substantially no odor.
The 2-hydroxymethyl-cyclopentanol derivatives of the formula (9) to be employed in the present invention include compounds derived by adding a saturated straight-chain or branched alkyl group having 1-12 carbon atoms to the second carbocyclic atom of a 2-hydroxymethyl-cyclopentanol, such as:
2-hydroxymethyl-2-methyl-cyclopentanol,
2-hydroxymethyl-2-ethyl-cyclopentanol,
2-hydroxymethyl-2-propyl-cyclopentanol,
2-hydroxymethyl-2-isopropyl-cyclopentanol,
2-hydroxymethyl-2-butyl-cyclopentanol,
2-hydroxymethyl-2-hexyl-cyclopentanol,
2-hydroxymethyl-2-octyl-cyclopentanol,
2-hydroxymethyl-2-decyl-cyclopentanol,
2-hydroxymethyl-2-dodecyl-cyclopentanol,
and the like.
The substituent alkyl group at the second carbocyclic atom is preferred to have about 1-8 carbon atoms in view of the volatility of the compounds.
The 2-hydroxymethyl-3-methyl-6-isopropyl-cyclohexanol, that is, 2-hydroxymethyl-menthol (referred to as xe2x80x9cHMMOxe2x80x9d hereinafter) shown by the chemical formula (7), which is applied in the present invention, can be produced by a manufacturing process wherein 2-ethoxycarbonyl-menthone is obtained from menthone and diethyl carbonate, and then reduced.
The HMMO obtained by the above synthesizing process is a colorless, transparent, oily substance having substantially no odor.
The 2-hydroxymethyl-cycloalkanol derivatives shown by the general structural formula (6), which are employed in the present invention, can be produced by reducing, with lithium borohydride, a 2-ethoxycarbonyl cycloalkanone which has been obtained by a conventional process from a cycloalkanone comprising a straight-chain or branched, saturated, substituent hydrocarbon radical having 0-8 total carbon atoms added to a carbocyclic atom thereof (Organic Synthesis, Vol. 47, p. 20, 1967).
The 2-hydroxymethyl-cycloalkanol derivatives obtained by the above synthesizing process is a colorless, transparent, oily substance having substantially no odor.
The 2-hydroxymethyl-cycloalkanol derivatives of the formula (6), which are employed in the present invention, include 2-hydroxymethyl-cycloalkanols comprising a 5-12-membered carbocycle and such compounds further comprising at least one saturated, straight-chain or branched alkyl substituent group having 1-8 total carbon atoms added to the carbocyclic atoms thereof, such as:
2-hydroxymethyl-3-methyl-cyclopentanol,
2-hydroxymethyl-3-ethyl-cyclopentanol,
2-hydroxymethyl-4-propyl-cyclopentanol,
2-hydroxymethyl-4-isopropyl-cyclopentanol,
2-hydroxymethyl-4-methyl-cyclohexanol,
2-hydroxymethyl-5-methyl-cyclohexanol,
2-hydroxymethyl-6-methyl-cyclohexanol,
2-hydroxymethyl-4-ethyl-cyclohexanol,
2-hydroxymethyl-4-(t-butyl)-cyclohexanol,
2-hydroxymethyl-6-(t-butyl)-cyclohexanol,
2-hydroxymethyl-6-(sec-butyl)-cyclohexanol,
2-hydroxymethyl-4-(t-amyl)-cyclohexanol,
2-hydroxymethyl-3,4-dimethyl-cyclohexanol,
2-hydroxymethyl-4,5-dimethyl-cyclohexanol,
2-hydroxymethyl-3,3,5-trimethyl-cyclohexanol,
2-hydroxymethyl-3,5,5-trimethyl-cyclohexanol,
2-hydroxymethyl-cycloheptanol,
2-hydroxymethyl-cyclooctanol,
2-hydroxymethyl-2-ethyl-cyclooctanol,
2-hydroxymethyl-cyclododecanol,
and the like.
The manufacturing process of the 2-(1-hydroxyalkyl)-cycloalkanol derivatives to be employed in the present invention is not specifically limited. The 2-(1-hydroxyalkyl)-cycloalkanol derivatives can be produced by reducing, with a reducing agent such as lithium borohydride, a 2-(1-hydroxyalkyl)-cycloalkanone derivative which has been obtained by a conventional process from an aldehyde and a 2-bromocycloalkanone derivative comprising a straight-chain or branched, saturated substituent hydrocarbon radical having 0-8 total carbon atoms added to the carbocyclic atom thereof (J. Amer. Chem. Soc., Vol. 89, p. 5727, 1967).
The above 2-(1-hydroxyalkyl)-cycloalkanol derivatives include 2-(1-hydroxyalkyl)-cycloalkanols comprising a 5-12-membered carbocycle and these compounds further comprising at least one saturated, straight-chain or branched alkyl substituent group having 0-8 total carbon atoms added to the carbocyclic atoms thereof, such as:
2-(1-hydroxyethyl)-3-methyl-cyclopentanol,
2-(1-hydroxybutyl)-3-ethyl-cyclopentanol,
2-(1-hydroxyethyl)-4-propyl-cyclopentanol,
2-(1-hydroxypropyl)-4-ethyl-cyclopentanol,
2-(1-hydroxyethyl)-4-methyl-cyclohexanol,
2-(1-hydroxyamyl)-5-methyl-cyclohexanol,
2-(1-hydroxyethyl)-6-methyl-cyclohexanol,
2-(1-hydroxybutyl)-4-ethyl-cyclohexanol,
2-(1-hydroxyethyl)-3-methyl-cyclohexanol,
2-(1-hydroxybutyl)-6-methyl-cyclohexanol,
2-(1-hydroxyethyl)-3-methyl-6-isopropyl-cyclohexanol,
2-(1-hydroxybutyl)-4-isopropyl-cyclohexanol,
2-(1-hydroxyethyl)-3,4-dimethyl-cyclohexanol,
2-(1-hydroxyethyl)-4,5-dimethyl-cyclohexanol,
2-(1-hydroxybutyl)-cycloheptanol,
2-(1-hydroxyethyl)-cyclooctanol,
2-(1-hydroxybutyl)-cyclooctanol,
2-(1-hydroxyethyl)-cyclodecanol,
and the like.
The 3-(1-hydroxyalkyl)-borneol derivatives shown by the general formula (10), to be employed in the present invention, can be regarded as a specific structure which, in the 2-(1-hydroxyisoalkyl)-6-methyl-hexanol falling in the scope of the general formula (1), is specified by defining n as 4 and the third and sixth carbocyclic atoms thereof are intramolecularly bridged with an isopropylidene group. These are known compounds. These compounds can be produced by reducing, with a reducing agent such as lithium aluminum hydride, sodium borohydride or the like, 3-(1-hydroxyalkyl)-camphor derivatives which can be prepared according to the process disclosed in J. Org. Chem. Vol. 56, p. 378-387 (1991).
The 3-(1-hydroxyalkyl)-borneol derivatives to be employed in the present invention include:
3-(1-hydroxymethyl)-borneol,
3-(1-hydroxyethyl)-borneol,
3-(1-hydroxypropyl)-borneol,
3-(1-hydroxy-1-methylethyl)-borneol,
3-(1-hydroxybutyl)-borneol,
3-(1-hydroxy-1-methylpropyl)-borneol, and
3-(1-hydroxy-2-methylpropyl)-borneol.
These compounds are substantially odorless.
Among the 2-(1-hydroxyisopropyl)-cycloalkanone derivatives of the general structural formula (12) which fall in the scope of the above general structural formula (11), the 2-(1-hydroxyisopropyl)-5-methyl-cyclopentanone shown by the chemical formula (13) can be produced by oxidizing 2-(1-hydroxyisopropyl)-5-methyl-cyclopentanol, which can be prepared according to the process disclosed in Japanese Patent Application Kokai No. 3-250,533, with a salt or oxide of a metal, such as chromium, manganese, silver or the like, or an organic oxidizing agent (dimethyl sulfoxide or the like). The thus obtained 2-(1-hydroxyisopropyl)-5-methyl-cyclopentanone is a substantially odorless, pale yellow, oily substance.
Similarly, the 8-hydroxy-p-menthan-3-one derivatives shown by the general formula (14) which fall in the scope of the chemical formula (12) can be produced by oxidizing, with a salt or oxide of a metal, such as chromium, manganese, silver or the like, a metal oxide thereof or an organic oxidizing agent (dimethyl sulfoxide or the like), a diol which can be prepared by admixing a 3,7-dimethyl-6-octenal derivative having a substituent hydrocarbon radical at the second carbon atom thereof with an aqueous solution of an acid such as sulfuric acid or the like, while stirring. The thus obtained 8-hydroxy-p-menthan-3-one derivatives are substantially odorless, colorless and transparent, oily substances.
The above 8-hydroxy-p-menthan-3-one derivatives include:
8-hydroxy-2-methyl-p-menthan-3-one,
8-hydroxy-2-methylene-p-menthan-3-one,
8-hydroxy-2-ethyl -p-menthan-3-one,
8-hydroxy-2-propyl-p-menthan-3-one,
8-hydroxy-2-isopropyl-p-menthan-3-one,
8-hydroxy-2-butyl-p-menthan-3-one,
8-hydroxy-2-isobutyl-p-menthan-3-one,
8-hydroxy-2-hexyl-p-menthan-3-one,
8-hydroxy-2-(2-ethylhexyl)-p-menthan-3-one,
8-hydroxy-2-(2-propenyl)-p-menthan-3-one,
8-hydroxy-2-(3-pentenyl)-p-menthan-3-one,
8-hydroxy-2-(2-propenyl)-p-menthan-3-one,
and the like.
The manufacturing process of the 2-hydroxymethyl-cycloalkanone derivatives shown in the general structural formula (16) which are employed in the present invention is not specifically limited. The 2-hydroxymethyl-cycloalkanone derivatives can be produced by reducing selectively an ethoxycarbonyl group of a 2-ethoxycarbonyl cycloalkanone derivative which has been obtained by a conventional process from a cycloalkanone comprising a straight-chain or branched, saturated substituent hydrocarbon radical having 0-12 total carbon atoms added to a carbocyclic atom thereof (Chem. Pharm. Bull., Vol. 29, No. 10, p. 3047, 1981).
The 2-hydroxymethyl-cycloalkanone derivatives of the general structural formula (16) include 2-hydroxymethyl-cycloalkanone comprising a 5-12-membered carbocycle and such compounds further comprising at least one saturated, straight-chain or branched, substituent hydrocarbon radical having 0-12 total carbon atoms added to the carbocyclic atom thereof, such as:
2-hydroxymethyl-3-methyl-cyclopentanone,
2-hydroxymethyl-3-ethyl-cyclopentanone,
2-hydroxymethyl-4-propyl-cyclopentanone,
2-hydroxymethyl-4-isopropyl-cyclopentanone,
2-hydroxymethyl-4-methyl-cyclohexanone,
2-hydroxymethyl-5-methyl-cyclohexanone,
2-hydroxymethyl-6-methyl-cyclohexanone,
2-hydroxymethyl-4-ethyl-cyclohexanone,
2-hydroxymethyl-4-(t-butyl)-cyclohexanone,
2-hydroxymethyl-6-(t-butyl)-cyclohexanone,
2-hydroxymethyl-6-(sec-butyl)-cyclohexanone,
2-hydroxymethyl-4-amyl-cyclohexanone,
2-hydroxymethyl-3,4-dimethyl-cyclohexanone,
2-hydroxymethyl-4,5-dimethyl-cyclohexanone,
2-hydroxymethyl-cycloheptanone,
2-hydroxymethyl-cyclooctanone,
2-hydroxymethyl-2-ethyl-cyclooctanone,
2-hydroxymethyl-cyclododecanone,
and the like.
These compounds are substantially odorless.
The 2-(hydroxymethyl)-3-methyl-6-isopropyl-cyclohexanone shown in the chemical formula (17) which is employed in the present invention, that is, 2-hydroxymethyl-menthone (referred to as xe2x80x9cHMMTxe2x80x9d hereinafter), can be manufactured by heating, while stirring, menthone and formaldehyde in methanol in the presence of potassium carbonate.
According to the above synthesizing process, the HMMT that is a substantially odorless and colorless, transparent, oily substance is produced.
The manufacturing process of the 2-(1-hydroxyalkyl)-cycloalkanone derivatives shown by the general structural formula (15) which are employed in the present invention, is not specifically limited. The 2-(1-hydroxyalkyl)-cycloalkanone derivatives can be produced according to a conventional process from a 2-bromocycloalkanone derivative having a straight-chain or branched, saturated substituent hydrocarbon radical comprising 0-12 total carbon atoms added to a carbocyclic atom thereof and an aldehyde (J. Amer. Chem. Soc., Vol. 89, p. 5727, 1967).
The 2-(1-hydroxyalkyl)-cycloalkanone derivatives include 2-(1-hydroxyalkyl)-cycloalkanones comprising a 5-12-membered carbocycle and such compounds further comprising at least one saturated, straight-chain or branched, substituent hydrocarbon radical of 0-12 total carbon atoms added to the carbocyclic atom(s) thereof, such as:
2-(1-hydroxyethyl)-3-methyl-cyclopentanone,
2-(1-hydroxybutyl)-3-ethyl-cyclopentanone,
2-(1-hydroxyhexyl)-4-propyl-cyclopentanone,
2-(1-hydroxypropyl)-4-ethyl-cyclopentanone,
2-(1-hydroxyamyl)-4-methyl-cyclohexanone,
2-(1-hydroxyethyl)-3,5-dimethyl-cyclohexanone,
2-(1-hydroxyethyl)-6-methyl-cyclohexanone,
2-(1-hydroxybutyl)-1-ethyl-cyclohexanone,
2-(1-hydroxyethyl)-3-methyl-cyclohexanone,
2-(1-hydroxybutyl)-6-methyl-cyclohexanone,
2-(1-hydroxyethyl)-3-methyl-6-isopropyl-cyclohexanone,
2-(1-hydroxybutyl)-4-isopropyl-cyclohexanone,
2-(1-hydroxyethyl)-3,4-dimethyl-cyclohexanone,
2-(1-hydroxyethyl)-4,5-dimethyl-cyclohexanone,
2-(1-hydroxybutyl)-cycloheptanone,
2-(1-hydroxyethyl)-cyclooctanone,
2-(1-hydroxybutyl)-cyclooctanone,
2-(1-hydroxyethyl)-cyclododecanone,
and the like.
These compounds are substantially odorless.
The 3-(1-hydroxyalkyl)-.camphor derivatives of the general structural formula (18), which are employed in the present invention, can be regarded as a specific structure which, in the 2-(1-hydroxy-isoalkyl)-6-methyl-hexanone shown by the general structural formula (13), is specified by defining n as 4 and the third and sixth carbocyclic atoms thereof are intramolecularly bridged with an isopropylidene group. These are known compounds. These compounds can be manufactured according to the process disclosed in J. Org. Chem., Vol. 56, p. 378-387 (1991). However, the manufacturing process is not specifically limited.
Such 3-(1-hydroxyalkyl)-camphor derivatives include:
3-(1-hydroxymethyl)-camphor,
3-(1-hydroxyethyl)-camphor,
3-(1-hydroxypropyl)-camphor,
3-(1-hydroxy-1-methyethyl)-camphor,
3-(1-hydroxybutyl)-camphor,
3-(1-hydroxy-1-methylpropyl)-camphor, and
3-(1-hydroxy-2-methylpropyl)-camphor.
These compounds are substantially odorless.
There are several stereoisomers to be applied to the present invention. However, when they are used as a noxious-insect repellent, they can be in either a singular stereoisomeric form or a mixture. From these compounds, cis and trans forms can be isolated by a column treatment or the like and separated as crystals. All of these isomers have an excellent repelling effect against noxious-insects such as mosquitoes.
These compounds to be used in the present invention are all substantially odorless.
Noxious-insect repellent compositions in various dosage forms can be prepared by blending the above-described compound as an active ingredient with a base of cosmetics or pharmaceuticals which are usually applied to human bodies or animals. They can be formulated in, for example, lotions, aerosols, milky lotions, creams or the like. These compounds can be further incorporated with other noxious-insect repellents, antioxidants, UV-absorbers, humectants or other additives.
The above compounds or the above prepared compositions of the present invention can be applied directly to human bodies or animals. Besides, substrates, such as sheets, films, nets or the like, which have preliminarily been treated with the above compound or composition by means of application, impregnation or blending, can also be used.
The quantity of the above compounds to be formulated in the noxious-insect repellents depends upon the dosage form, usage or other conditions. However, it is preferred to be generally 0.1-90%, more preferably 3-20%, by weight. The noxious-insect repellents according to the present invention are used effectively against noxious-insects, such as mosquitoes such as tiger mosquitoes, Aedes albopictus; black flies; ticks; millipedes; armyworms; slugs; and the like.